2 tasks BZ, version 23, MTUCI

Objective 1
Draw a diagram of a three-phase four-wire network with grounded neutral and connected equipment. Show on the scheme: the breakdown in the body of the equipment; protection against breakdown of the housing through nulling; re-grounding neutral conductor; current protection equipment
1. Determine the stress on the body of equipment for the closure phase housing:
a) for Vanishing equipment (connecting buildings to the neutral conductor);
b) re-grounding neutral conductor.
2. Determine the short-circuit current and check whether it satisfies the condition for PES blown fuse link:
Isc ≥In,
Where In- current fuse, check for In = 20, 30, 50, 100 A
3. Identify potential buildings for the closure phase for open and grounded neutral (before and after the break)
4. Determine the current passing through the human body, concerning the closure of the equipment phase to the body:
a) without re-grounding neutral conductor;
b) re-grounding neutral conductor.
5. Determine the touch voltage on the body vanishing installation by closing one of the phases to earth
6. Calculate the grounding device, consisting of n individual grounding so that rg does not exceed 4 ohms.
7. Formulate conclusions.
Initial data:
Uf = 220
Rp = 20 ohms
Zp = 1.6 ohm
Zl = 0.9 ohm
Rzm = 100 ohms
l = 2,0 m
d = 0,07 m
t = 2,0 m
ηz = 0.69 m
Kind of Soil - supesok
ρ = 300 ohm ∙ m

Task 2
The production laboratory carried out technical operations related to soldering. To capture and remove harmful contaminants (lead, tin, and others.) Directly from their place of education must be installed local exhaust ventilation. Removal of polluted air is carried out with the help of special devices - umbrellas mounted above the desktop. According to the known characteristics of the solder, the number of rations per hour, the speed of the air intake of harmful substances in the problem must determine:
1. The amount of lead released during soldering.
2. Hourly amount of air needed to remove lead fumes
3. The size of the umbrella (the area) for optimal local ventilation.
According to the results of calculations to draw conclusions.
Initial data:
POS-50
r = 2,0%
R = 0,10 g
N = 50 1 / h
V = 1,20 m / s